Shock absorber for aircraft



Sept. l., 1936. F LANDGRAF Y A 2,652,775

SHOCK ABSORBER FOR AIRCRAFT Filed July 1, 1935 INVENTOR ATTORNEY.

Patented Sept. l, 1936 UNITED lSTATE-s PATENT oI-FICE American ys,

poration of Colorado Inc., Denver, Colo., a cor- Applicauon July ,1, 1935, serial No. 29,300

This invention relates to a shock absorbing device, more particularly designed to absorb the shock of the landing wheels of an aircraft. The

principal object of the inventionls toprovide aA light, compact, highly efficient absorbing device in which the absorption or resistance will gradf ually increase as the shocki increases, and in which all packing, stuiiing, boxes, and other'devices to prevent iiuid leakageare eliminated.

Other objects and advantages reside in the detail construction of the invention, whichis designed for simplicity, economy, and eiliclency.

These will become more apparent from the following description.

In the following detailed description of the invention reference is hadvto the accompanying drawing which forms a part hereof. Like numerals refer to like partsin all views of the draw- Fig. 6 is a detail enlarged section through the upper portion of the cylinder.

Fig. 7'is a detail face view of the check valve plate.

In Fig.. 1, a portion of a typical landing gear of an aircraft is indicated at ID and one of the landing wheels is illustrated at II with its axle support at I5.

The landing gear I0 carries a downwardly projecting outer cylindervI2 which is open at its bottom, and closed at its top by means of a head plate I3. An inner cylinder, which will be herein v designated the piston cylinder I4,\is secured to .the axle member I5 of the landing wheel II. The piston cylinder I4 is closed at its bottom and is open at its top and is of a-diameter to iit snugly within the outer cylinder I2.

A hollow piston tube I6 is secured to the head plate I3 by means of a threaded check valve housing I1. The lower extremity of the piston tube IB terminates in a threaded piston I8. Ports 33 are formed in the tube I6 adjacent the bottom thereof.

l At a point on the interior surface of the piston cylinder I4, inwardly projecting threads 2| are formed into whi'ch a partition bushing 22 is threaded, The bushing 22 is provided with wrench sockets 23 to facilitate its insertion. A 5 compression spring 24 rests upon the partition bushing 22 and normallyterminates below the head plate I3, as shown in Fig. 1.

In assembling the device the piston I8 is first vplaced in the cylinder I4 and rotated to thread 10 it past and-below the threads 2l. 'Ihe bushing 22 is then dropped into the cylinder I4 about the piston rod I6 and threaded tight into the threads The threads on the bushing terminate below its top so that it can not thread past the threads 15 2|. The spring 24 is then placed about the tube I6, and the entire assembly is forced upwardly into the cylinder I2. 'I'he check valve housing I'I is then threaded into the top of the piston tube to hold the entire assemblyin place. A threaded bushing 25 is welded, brazedfor otherwise secured in the top of the piston tube I6 to receive the valve housing I'l.

A check valve plate I9 is held In the piston I8 by means of a spring ring 20. 'This plate is formed with an annular series of perforations 26 adjacent its edge and a central perforation 21.

yThe check valve housing 'I1 contains a check valve ball 28 which prevents inow into the housing. The ball is retained in the housing by means o of a suitable cross pin 29. Ports 38 are formed below the valve ball 28 which communicate with passages 3| through the piston rod I6. 'Ihe head of the valve housing is drilled radially as shown at 32 to receive a cotter key or locking wire to prevent accidental unscrewing of the housing.

In use, the lower part of the piston cylinder I4 is iilled with oil or other suitable fluid. While the aircraft is in the air, so that there is no weight on the landing wheel I I, the parts will be in the position illustrated in Fig. 1. When the landing wheel rst contacts with the ground, the piston cylinder I4 will be pushed into the cylinder I2. This forces oilfrom the lower portion of the cylinder I4 through the ports 26 and 21 in the check valve plate I9 into the hollow piston tube I8. From thence, the oil ows through the ports 33 into the cylinder I2.

As -the pressure` on the wheel increases, the ow of oil will force the check valve plate I9 againstits seat in the piston I8 so as to close the perforations 26 and restrict the flow to the single perforation 21 which increases the resistance or absorbtion, and allows the cylinder I4 to move upwardly more slowly until the spring 24 con- 55 tacts with the head I3. At this time, the resistance of the spring will be added to the resistance of the oil so as to absorb the maximum shock.

The oil flowing into the cylinder I2 will compress air in the upper part thereof. This air will exit through the ports 3l and passages 30 past the check ball 28. When the cylinder I4 moves downward on the rebound, the ball 28 will close so as to produce a partial vacuum in the cylinder I2. `This vacuum will draw air inwardly between the two cylinders so as to remove any extruded oil from between the cylinders and prevent leakage about the cylinder I4. This eliminates the necessity for packing to prevent oil leakage.

A sleeve 34 surrounds the piston tubeadjacentv the piston I8. The opening in the bushing 22 ts snugly about this sleeve. When the tube I4 is dropping to the bottom on a rebound the oil will flow from the upper cylinder through the bushing about the piston tube.- As the bottom is approached the sleeve 34 will restrict the bushing opening to check the returning oil and provide a rebound cushion. The threads about the piston I8 serve as oil sealing grooves.

While 'a specic form of the improvement has been described and illustrated herein, it is desired to be understood that the same may be varied, within the scope of the appended claims, without departing from the spirit ofthe invention.

Having thus described the invention, what is claimed and desired secured by Letters Patent 1. A shock absorber for aircraft comprising: a rst downwardly extending open bottomed cylinder; means for securing said cylinder to said aircraft; a second upwardly extending open topped cylinder; means for securing said latter cylinder to a landing wheel; a head in said first 40 cylinder; a piston tube extending downwardly inder; means for securing said cylinder to saidv aircraft;l a second upwardly extending open topped cylinder; means for securing said latter cylinder to a landing wheel; a head in said rst cylinder; a `piston tube extending downwardly within said cylinders from said head; a piston on the lower extremity of said piston tube closing said second cylinder; a partition plate surrounding said piston tube above said piston; a com-v pression spring surrounding said piston tube. between said partition plate and said head; and means' for creating a partial vacuum in said rst cylinder. y

3. A- shock absorber for aircraft comprising:

a first downwardly extending open bottomed cyll inder; 'means for securing said cylinder to said aircraft; a second upwardly extending open topped cylinder; means for securing said latter cylinder to a landing wheel; a head in said first cylinder; a piston tube extending downwardly within said cylinders from said head; a piston on the lower extremity of said piston tube'closing said second cylinder; a partition plate surrounding said piston tube abovesaid piston, said piston tube being hollow and provided with passages communicatingv with the interior of said first cylcylinder; a piston tube extending downwardly f' within said cylinders from said head; a. piston on the lower extremity of said piston tube closing said secon'd cylinder; a partition plate surrounding said piston tube above said piston; said piston t tubev opening through said head; a valve housing in the upper extremity of said piston tube; and a check valve in said housing to allow exit of air from said first cylinder and to prevent return of air thereto.

5. A shock absorber comprising: two tubes, each open at its one extremity and closed at its other extremity, the open extremity of the second tube tting snugly into the open extremity of vthe rst tube so that their walls are in slidable contact throughout their length; a partition intermediate the extremities-of said second tube; a piston tube extending from the closed extremity of said irst 'tube through said partition and terminating in said second tube; a piston on the latter extremity of said piston tube; a restricted passage between` the interiors of said tubes through said piston tube; a compression spring surrounding said piston tube and positioned above the partition and within said second tube; a uid in said second tube; and means for allowing air to escape from said first tube as the uid enters from said second tube but preventing air from returning so as'to create a-vacuum therein to prevent leakage between said slidably contacting tubes.

FRED LANDGRAF. 

